Interferential Therapy (IFT)

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Interferential Therapy (IFT)

• Project search by
• Omar Jarrah
• 200311084

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Description

• Interferential therapy consists of the
  superposition, over the pathological area, of two
  identical radiations but with slightly different
  frequencies, which originate waves of low
  frequency and with modulated amplitude. The
  generation of an interferential field with a
  therapeutic objective has been used only through
  the superposition of alternating currents of
  medium frequency in a range 1-10 KHz, called
  interferential electric therapy

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• However, there are no precedents of a device that
  allows generation of an interferential field with
  ultrasonic origin, through the use of two
  independent ultrasound transducers with
  simultaneous use and slightly out-of-step
  frequency. This technology has generated a
  prototype of interferential ultrasonic therapy,
  which allows therapeutic application in articular
  pathology and skeletal muscle with interferential
  form, through the simultaneous use of two
  independent transducers.

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Current and Potential Domain of Application

• This technology is used as therapeutic agent,
  anti-inflammatory, analgesic and osteogenesis,
  based on the mechanical and thermal effects of
  ultrasounds on the body.

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Introduction IFT Production

• The basic principle of Interferential Therapy
  (IFT) is to utilize the strong ?physiological
  effects of low frequency (lt250pps) electrical
  stimulation of nerves without the associated
  painful and somewhat unpleasant side effects
  sometimes associated with low frequency stem.
• The effects of tissue stimulation with these
  'medium frequency' currents (medium frequency in
  electro medical terms is usually considered to be
  1KHz-100KHz) has yet to be established. It is
  unlikely to do nothing at all, but in terms of
  current practice, little is known of its
  physiological effects.

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• The exact frequency of the resultant beat
  frequency can be controlled by the input
  frequencies. If for example, one current was at
  4000Hz and its companion current at 3900Hz, the
  resultant beat frequency would be at 100Hz,
  carried on a medium frequency 3950Hz amplitude
  modulated current.

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Frequency Sweep Nerves

• will accommodate to a constant signal a sweep
  (or gradually changing frequency) is often used
  to overcome this problem. The principle of using
  the sweep is that the machine is set to
  automatically vary the effective stimulation
  frequency using either pre-set or user set sweep
  ranges. The sweep range employed should be
  appropriate to the desired physiological effects
  (see below). It has been repeatedly demonstrated
  that wide sweep ranges are ineffective in the
  clinical environment

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• Note Care needs to be taken when setting the
  sweep on a machine in that with some devices, the
  user sets the actual base and top frequencies
  (e.g. 10 and 25Hz) and with other machines the
  user sets the base frequency and then how much
  needs to be added for the sweep (e.g. 10 and
  15Hz).

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• The pattern of the sweep makes a significant
  difference to the stimulation received by the
  patient. Most machines offer several sweep
  patterns, though there is very limited evidence
  to justify some of these options. In the classic
  triangular sweep pattern, the machine gradually
  changes from the base to the top frequency,
  usually over a time period of 6 seconds though
  some machines offer 1 or 3 second options. In the
  example illustrated, the machine is set to sweep
  from 90 to 130Hz (figure A) employing a
  triangular sweep pattern. All frequencies between
  the base and top frequencies are delivered in
  equal proportion.

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The diagram (figure B) illustrates the effect of
setting a 90 130Hz rectangular sweep.
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Physiological Effects Clinical Applications

• It has been suggested that IFT works in a
  special way because it is interferential as
  opposed to normal stimulation. The evidence for
  this special effect is lacking and it is most
  likely that IFT is just another means by which
  peripheral nerves can be stimulated. It is rather
  a generic means of stimulation the machine can
  be set up to act more like a TENS type device or
  can be set up to behave more like a muscle
  stimulator by adjusting the stimulating (beat)
  frequency. It is often regarded (by patients) to
  be more acceptable as it generates less
  discomfort than some other forms of electrical
  stimulation.
• The clinical application of IFT therapy is based
  on peripheral nerve stimulation (frequency) data,
  though it is important to note that much of this
  information has been generated from research with
  other modalities, and its transfer to IFT is
  assumed rather than proven. There is a lack of
  IFT specific research compared with other
  modalities (e.g. TENS).

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Muscle Stimulation

• Stimulation of the motor nerves can be achieved
  with a wide range of frequencies. Clearly,
  stimulation at low frequency (e.g. 1Hz) will
  result in a series of twitches, whist stimulation
  at 50Hz will result in a tetanic contraction.
  There is limited evidence at present for the
  strengthening effect of IFT (though this
  evidence exists for some other forms of
  electrical stimulation), though the paper by
  Bircan et al (2002) suggests that it might be a
  possibility. On the basis of the current
  evidence, the contraction brought about by IFT is
  no better than would be achieved by active
  exercise, though there are clinical circumstances
  where assisted contraction is beneficial. For
  example to assist the patient to appreciate the
  muscle work required (similar to surged Faradism
  used previously but much less uncomfortable).
  For patients who can not generate useful
  voluntary contraction, IFT may be beneficial as
  it would be for those who, for whatever reason,
  find active exercise difficult. There is no
  evidence that has demonstrated a significant
  benefit of IFT over active exercise.

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Blood flow

• There is very little, if any quality evidence
  demonstrating a direct effect if IFT on local
  blood flow changes. Most of the work that has
  been done involves laboratory experimentation on
  asymptomatic subjects, and most blood flow
  measurements are superficial i.e. skin blood
  flow. Whether IFT is actually capable of
  generating a change (increase) in blood flow at
  depth remains questionable. The elegant
  experimentation by Noble et al (2000)
  demonstrated vascular changes at 1020Hz, though
  was unable to clearly identify the mechanism for
  this change.

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Oedema

• IFT has been claimed to be effective as a
  treatment to promote the reabsorption of oedema
  in the tissues. Again, the evidence is very
  limited in this respect and the physiological
  mechanism by which is could be achieved as a
  direct effect of the IFT remains to be
  established. The preferable clinical option in
  the light of the available evidence is to use the
  IFT to bring about local muscle contraction(s)
  which combined with the local vascular changes
  that will result (see above) could be effective
  in encouraging the reabsorption of tissue fluid.
  The use of suction electrodes may be beneficial,
  but also remains unproven in this respect.

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Treatment Parameters

• Stimulation can be applied using pad electrodes
  and sponge covers (which when wet provide a
  reasonable conductive part), though electro
  conductive get is an effective alternative. The
  sponges should be thoroughly wet to ensure even
  current distribution. Self adhesive pad
  electrodes are also available (similar to the
  newer TENS electrodes) and make the IFT
  application easier in the view of many
  practitioners. The suction electrode application
  method has been in use for several years, and
  whilst it is useful, especially for larger body
  areas like the shoulder girdle, trunk, hip, knee,
  it does not appear to provide any therapeutic
  advantage over pad electrodes (in other words,
  the suction component of the treatment does not
  appear to have a measurable therapeutic effect.
  Care should be taken with regards maintenance of
  electrodes, electrode covers and associated
  infection risks (Lambert et al 2000).

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Interferential Treatment Record

• Electrode number (2 pole, 4 pole) and positions
  
• Frequency applied
• Sweep settings employed (if applicable)
• Current intensity applied (or patient reported
  sensation)
• Treatment duration

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Interferential Contraindications

• Patients who do not comprehend the
  physiotherapists instructions or are unable to
  co-operate should not be treated
• Patients who are taking anticoagulation therapy
  or have a history of pulmonary embolism or deep
  vein thrombosis should not be treated with the
  vacuum electrode applications
• Similarly, patients whose skin may be easily
  damaged or bruised
• Application over
• The trunk or pelvis during pregnancy
• Active or suspected malignancy except in
  hospice care
• The eyes

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• The anterior aspect of the neck
• The carotid sinuses
• Patients with pacemakers
• Dermatological conditions e.g. dermatitis,
  broken skin
• Danger of haemorrhage or current tissue
  bleeding (e.g. recent soft tissue injury)
• Avoid active epiphyseal regions in children
• Transthoracic electrode application is
  considered to be risky by many authorities

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Interferential Precautions

• Care should be taken to maintain the suction at
  a level below that which causes damage /
  discomfort to the patient
• If there is abnormal skin sensation, electrodes
  should be positioned in a site other than this
  area to ensure effective stimulation
• Patients who have (marked) abnormal circulation
  
• For patients who have febrile conditions, the
  outcome of the first treatment should be
  monitored

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• Patients who have epilepsy, advanced
  cardiovascular conditions or cardiac arrhythmias
  should be treated at the discretion of the
  physiotherapist in consultation with the
  appropriate medical practitioner
• Treatment which involves placement of
  electrodes over the anterior chest wall